Implants are commonly used for orthopaedic and dental applications. There is however a problem with implants; they have a tendency to get loose after 10-15 years of usage. Bone that is not used will get weaker; this can be concluded from studies of people being immobilised or in microgravity. When an implant is put into bone, the surrounding bone does not experience any deformation and it will resorb. This is called stress shielding. Finally the implant will get loose. To avoid this problem we want to give electrical stimulation to the bone surrounding the implant. Electricity has been used before to stimulate bone, and it has been shown that immobilised bone can almost be maintained by using electric stimulation. Piezoelectricity is a property of certain materials that make them generate electricity when they are deformed. When an implant is coated with a piezoelectric material, electrical stimulation can be achieved for the surrounding bone that is stress shielded. In this diploma work, a test-equipment is built to stimulate cells. Cells will be grown on a piezoelectric plate that is bent by the test-equipment. Thus, the cells will be stimulated by both mechanical stress and electric potential since the piezoelectric material generates electricity when it is deformed. Piezoelectric samples and culture wells suitable for bending applications are prepared and tested in the equipment. Some initial cell growth experiments have been performed to see that the material is suitable for cell growth.

Orientadores: Pedro Duarte Novaes, Cristiane Ribeiro Salmon / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-20T00:19:31Z (GMT). No. of bitstreams: 1 Neves_JulianadosSantos_D.pdf: 4044530 bytes, checksum: 22df8d6b0c562b9ece71cf5970d118cc (MD5) Previous issue date: 2012 / Resumo: A administração intermitente do hormônio paratireóideo (PTH) promove um aumento da massa óssea, sendo atualmente utilizado no tratamento de osteoporose. Entretanto, poucos estudos têm avaliado os efeitos do PTH sobre o metabolismo do osso alveolar, e mais especificamente, no processo de reparo desta estrutura, podendo este surtir um efeito favorável na cicatrização da ferida alveolar. Considerando-se que o padrão de cicatrização da ferida do alvéolo de molares de ratos é similar ao de humanos e a sua relevância clínica, este estudo teve como objetivo analisar o efeito da administração intermitente do PTH sobre o reparo alveolar após exodontia de molares de ratos. Ratas Wistar de 200g tiveram seus primeiros molares inferiores extraídos e receberam injeções subcutâneas de 40 ?g/kg de hPTH(1-34) (grupo PTH) ou solução veículo (grupo controle) em dias intemitentes após a exodontia. Os animais foram sacrificados aos 3, 5, 7 e 11 dias após a cirurgia. Análises histomorfométricas do volume de osso recém-formado, número de osteoblastos e osteoclastos TRAP-positivos foram realizadas em cortes histológicos seriados. O Ligante do receptor ativador do fator nuclear ?? (RANKL), Sialoproteína óssea (BSP) e Osteopontina (OPN) foram localizadas no alvéolo em cicatrização por imunohistoquímica. A expressão dos genes de Colágeno 1 (Col1?1), Fosfatase alcalina (Alp), Fator de crescimento insulínico (Igf-1), Osteocalcina (Ocn), Bsp, Opn, Osteoprotegerina (Opg) e Rankl, foi analisada por qRT-PCR. A presença de osso recém-formado foi notada em alvéolos a partir de 5 dias de reparo em ambos os grupos. O volume de osso recém-formado foi significativamente maior no grupo PTH nos períodos de 5, 7 e 11 dias (p<0.05), acompanhado de um número maior de osteoblastos aos 5 dias de reparo (p<0.05). No grupo controle houve um aumento gradual na expressão de todos os genes estudados, com exceção de OPN, nos períodos após a cirurgia. De um modo geral, a expressão de Col1?1, Alp, Igf-1 e Ocn foi maior no grupo PTH nos períodos iniciais, seguido por um decréscimo significativo aos 7 dias de reparo comparado ao grupo controle. A expressão de Bsp foi similar em ambos os grupos, enquanto a expressão de Opn foi menor vi no grupo PTH aos 7 e 11 dias de reparo, com estas proteínas apresentando a mesma distribuição nas trabéculas ósseas em formação no interior do alvéolo. O número de osteoclastos TRAP-positivos foi similar em ambos os grupos em todos os períodos avaliados, assim como o padrão de marcação para RANKL. Entretanto, a razão dos genes Rankl:Opg foi maior no grupo PTH aos 11 dias de reparo, sugerindo que o PTH pode favorecer a osteoclastogênese a partir deste período. Conclui-se que o tratamento intermitente com hPTH (1-34) teve um efeito anabólico sobre o processo de reparo do osso alveolar de forma pontual aos 5 dias, estimulando o aumento no número de osteoblastos e da expressão de genes relacionados a diferenciação e produção de matriz por estas células, causando consequentemente, um aumento no volume de osso recém-formado no interior do alvéolo / Abstract: The intermittent administration of parathyroid hormone (PTH) promotes an increase in bone mass, and it is currently used to treat osteoporosis. However, few studies have evaluated the effects of PTH on the metabolism of the alveolar bone, and more specifically in the repair process of this structure, which may have a positive effect on alveolar wound healing. Considering that the pattern of the alveolar wound healing post molar extraction in rats is similar to that of the humans and its clinical relevance, this study aimed to analyze the effect of intermittent PTH administration on alveolar wound healing after extraction of rat molars. Wistar rats (200g) had their first molars extracted and received subcutaneous injections of 40 ?g/kg of hPTH (1-34) (PTH group) or vehicle solution (control group) in alternated days after the extraction. The animals were sacrificed at 3, 5, 7 and 11 days after surgery. Histomorphometric analysis of the volume of newly formed bone, number of osteoblasts and TRAP-positive osteoclasts were performed on serial histological sections. Receptor activator of nuclear factor ?? ligand (RANKL), bone sialoprotein (BSP) and osteopontin (OPN) were localized at the healing socket by immunohistochemistry. Collagen 1 (Col1?1), alkaline phosphatase (Alp), insulin growth factor (Igf-1), osteocalcin (Ocn), Bsp, Opn, osteoprotegerin (Opg) and Rankl gene expression was assessed by qRT-PCR. Newly formed bone was observed in sockets from 5 days of repair in both groups. The volume of newly formed bone was significantly higher in PTH group at 5, 7 and 11 days of repair (p <0.05). In the control group there was a gradual increase in the expression of all genes studied, except for Opn, through the periods of healing. Overall, the expression of Col1?1, Alp, Igf-1 and Ocn in the PTH group was higher at the initial periods, followed by a significant down-regulation at 7 days of repair compared to the control group. Bsp expression was similar in both groups, while Opn expression was down-regulated by PTH at 7 and 11 days of repair. Both proteins showed the same distribution on the forming trabeculae in the socket. The number of TRAP-positive osteoclasts was similar in both groups in all periods of repair, as well as the labeling pattern for RANKL. However, viii Rankl:Opg ratio was higher in the PTH group at 11 days of repair, suggesting that PTH may promote osteoclastogenesis from this period. In conclusion, the intermittent treatment with hPTH-(1-34) had an anabolic effect on the alveolar wound healing specifically at 5 days of repair, stimulating an increase on the osteoblast number and on the expression of genes related to the differentiation and production of bone matrix by these cells, thereby resulting in increased volume of newly formed bone in the healing socket / Doutorado / Histologia e Embriologia / Doutor em Biologia Buco-Dental

5 p. / Originally published: 2011 / Healthy bone growth and maintenance requires adequate calcium intake. You can meet your calcium needs from foods, beverages, and, if necessary, supplements.

We evaluated coxofemoral joints from museum specimens of: Vulpes lagopus; Vulpes vulpes; Vulpes velox; Nyctereutes procyonoides; Urocyon cinereoargenteus; Aenocyon [Canis] dirus; Canis latrans; Canis lupus lupus; Canis lupus familiaris; C. l. familiaris × latrans; and Canis dingo. Acetabular components included: fossa; articular surface; medial and lateral articular margins; and periarticular surfaces. Acetabular components variably revealed: osteophyte-like features; varying appearance of articular margin rims (especially contour changes); rough bone surfaces (especially fossa and articular surface); and surface wear. Proximal femoral components included: articular surface; articular margin; periarticular surfaces; and joint capsule attachment. Femoral components variably revealed: rough bone surface; bone loss; articular margin osteophyte-like features; caudal post-developmental mineralized prominence; and enthesophytes along the joint capsule attachment. Non-metric multidimensional scaling was used to analyze right-left asymmetric relationships between observed traits, across taxa. Significantly different acetabular trait asymmetry involved only C. latrans-C. l. familiaris; V. vulpes-N. procyonoides, and U. cinereoargenteus-N. procyonoides. There were no significant lateralized differences in proximal femoral traits involving modern canids, ancient and modern C. l. familiaris, or modern vulpines. Thus, the observations were strongly bilateral. We hypothesized high similarity of traits across taxa. The data confirm the hypothesis and strongly suggest broad and deep morphological and mechanistic conservation that almost certainly pre-existed (at least) all modern canids. Further zoological studies are needed to evaluate phylogenic implications in greater detail.

No description available.

Dados recentes mostram que o remodelamento ósseo está sujeito ao controle do SNC, com o SNS. Para tanto, avaliamos o (CLO) e a morfologia da (LE) do fêmur de camundongos de 21 dias de idade selvagens (WT) e Knockout (KO) para a2CAR, tratados, para mimetizar o hipertiroidismo (Hiper) ou tratados para indução do hipotiroidismo (Hipo). Os animais KO eutiroideos (Eut) apresentaram uma desorganização da ZP e aumento do número de CHM da LE. Nos animais WT, o Hipo promoveu redução do CLO, desorganização da ZP e diminuição do número de CHM. O Hipo promoveu efeitos contrários na LE dos animais KO em relação aos animais WT, sendo capaz de reverter, parcialmente, a desorganização da ZP dos camundongos KO Eut, além de resultar em maior número de CHM, em relação aos animais WT Hipo. Já o Hiper levou a aumento do número de CH nos animais WT e redução nos animais KO. Os animais KO Hiper apresentaram diminuição de CHM, quando comparados aos animais WT Hiper. Esses achados reforçam as hipóteses de que o SNS regula o CLO via a2CAR e que o HT e SNS interagem para regular o CLO. / Recent data show that bone remodeling is under control of the CNS, with the SNS. Thus, we evaluated the bone growth and the morphology of the femoral EGP of 21- day old female wild-type (WT) and a2CAR-/- mice (KO), treated to mimic hyperthyroidism (Hyper), or treated for hypothyroidism (Hypo). The euthyroid KO mice had a disorganization of PZ and increase in the number of MHC of the EGP. In WT animals, Hypo promoted a significant reduction in the BLG, PZ disorganization and a decreased number of MHC. Hypo promoted opposite effects in EGP of KO compared to WT mice. Hypo was able to partially revert the PZ disorganization observed in euthyroid KO, and resulted in a greater number of MHC compared to WT Hypo. On the other hand, Hyper caused an increase in the number of HC in WT mice and a reduction in KO mice. Furthermore, Hyper KO animals showed a reduction in the number of MHC, when compared to the Hyper WT mice. These findings support the hypothesis that the SNS regulates the BLG via a2CAR and that the interaction between SNS and TH can regulate the BLG.

Sabe-se que o hormônio tireoideano (HT) é essencial para o crescimento e desenvolvimento ósseos. No entanto, os mecanismos pelos quais o HT regula esses processos são pouco entendidos. Recentemente, o sistema nervoso simpático (SNS) foi identificado como um potente regulador do metabolismo ósseo. Estudos do nosso grupo mostraram que o HT interage com o SNS para regular a massa e estrutura ósseas, e que essa interação envolve a sinalização adrenoceptora &#945;2 (&#945;2-AR). Também identificamos a presença de todos os subtipos de adrenoceptores &#945;2 adrenérgicos, o &#945;2A- , &#945;2B- e &#945;2C-AR, na lâmina epifiseal (LE) de camundongos. Além disso, observamos que camundongos com inativação gênica isolada do &#945;2A-AR e &#945;2C-AR (&#945;2A-AR -/- e &#945;2C-AR -/- ) apresentam LEs desorganizadas, ossos longos mais curtos, e atraso na ossificação endocondral. Estudos in vivo revelaram, que as LEs de animais &#945;2A-AR -/- e &#945;2C-AR -/- respondem de forma diferente (do que as LEs de animais selvagens) ao excesso e deficiência de HT, o que sugere fortemente que o HT também interage com o SNS para regular o crescimento e o desenvolvimento ósseos. Através de um sistema de cultura de órgãos de ossos longos, o presente estudo teve como objetivo investigar se o HT interage com o SNS diretamente no esqueleto, para regular o crescimento linear ósseo, e se os receptores &#945;2 adrenérgicos estão envolvidos nessa interação. Assim sendo, avaliamos, in vitro, o crescimento linear ósseo de tíbias derivadas de embriões de camundongos (com 15 dias de vida intrauterina) selvagens (WT) e &#945;2C- AR -/- (KO) durante 6 dias. Vimos que as tíbias KO apresentam um menor crescimento longitudinal quando comparadas às tíbias WT, e que o tratamento com 10-8 M de triiodotironina (T3) diminuiu significativamente o crescimento longitudinal das tíbias WT, o que não foi visto nas tíbias KO. Vimos, ainda, que o tratamento com UK 14,304 (UK), um agonista &#945;2 não seletivo, induziu o crescimento longitudinal somente nas tíbias KO. A expressão de genes relacionados com a diferenciação terminal de condrócitos (Col X, IGF-1, Wnt-4 e Runx2) mostrou-se aumentada nas tíbias KO (quando comparada à expressão nas tíbias WT). O tratamento com T3, como esperado, estimulou a expressão desses genes nas tíbias WT, porém diminui a expressão nas amostras KO, chamando a atenção para a importância desses receptores na modulação das ações do T3. Observamos, ainda, que a ativação local dos &#945;2- ARs com o UK bloqueia a expressão desses genes relacionados à diferenciação dos condrócitos, além de bloquear os efeitos positivos do T3 (UK+T3) na expressão desses genes. Esses achados mostram que os receptores &#945;2 adrenérgicos atuam diretamente no esqueleto para controlar a diferenciação terminal dos condrócitos e, portanto, o crescimento longitudinal ósseo, além de permitirem uma interação com a via de sinalização do HT para controlar esses processos. Em conclusão, este estudo mostra que HT interage com o SNS, localmente no esqueleto, via sinalização &#945;2 adrenérgica, para modular o crescimento linear ósseo. / It is well known that thyroid hormone (TH) is essential for normal bone growth and development. However, the mechanisms by which TH regulates these processes are poorly understood. Recently, the sympathetic nervous system (SNS) was identified as a potent regulator of bone metabolism. In vivo studies by our group have shown that TH interacts with the SNS to regulate bone mass and structure, and that this interaction involves &#945;2 adrenoceptor (&#945;2-AR) signaling. We have also identified the presence of &#945;2A- , &#945;2B- e &#945;2C-AR subtypes in the epiphyseal growth plate (EGP) of mice. In addition, we have found that mice with isolated gene deletion of &#945;2A-AR and &#945;2C-AR (&#945;2A-AR -/- and &#945;2C- AR -/- ) show a disorganized EGP, shorter long bones and a delay in endochondral ossification (EO). In vivo studies revealed that the EGP of &#945;2A-AR -/- and &#945;2C-AR -/- animals respond differently (than those of wild-type animals), to TH excess and deficiency, which strongly suggests that TH also interacts with the SNS to regulate bone growth and development. Through a long bone organ culture system, the present study had the goal of investigating if TH interacts with the SNS directly in the skeleton, to regulate the longitudinal bone growth and if &#945;2-AR is involved in this process. Therefore, we evaluated the linear bone growth of tibias derived from 15.5-day-old WT and &#945;2C-AR -/- mouse embryos (E15.5) for 6 days. We have seen that the KO tibias showed a lower longitudinal growth when compared to WT tibias, and that treatment with 10-8 M triiodothyronine (T3) significantly decreased the longitudinal growth of the WT tibias, which was not seen in the KO tibias. We found that the treatment with UK 14.304 (UK), a non-selective &#945;2-agonist, induced the longitudinal growth only of the KO tibias. The expression of genes related to the terminal differentiation of chondrocytes (Col X, IGF-1, Wnt-4 and Runx2) was shown to be increased in the KO tibias (when compared to the expression in WT tibias). Treatment with T3, as expected, stimulated the expression of these genes in WT tibias, but decreased the expression in KO samples, highlighting the importance of these receptors in the modulation of T3 actions. We observed that the local ? 2 -AR activation by UK blocked the expression of these chondrocyte differentiation- related genes, in addition to blocking the positive effects of T3 (UK + T3) in the expression of these genes. These findings show that &#945;2 adrenoceptors act directly in the skeleton, to control the terminal differentiation of chondrocytes and, therefore, the longitudinal bone growth, in addition to allow an interaction with the TH signaling pathway to control these processes. In conclusion, this study shows that TH interacts with the SNS, locally in the skeleton, via &#945;2 adrenergic signaling, to modulate the longitudinal bone growth.

Sabe-se que o hormônio tireoideano (HT) regula o desenvolvimento e crescimento dos ossos. No estudo, investigamos se o HT interage com o sistema nervoso simpático (SNS) controlando o crescimento longitudinal ósseo (CLO), e se essa possível interação depende do &#945;2A-AR. Para tanto, avaliamos o efeito de 30 dias de hipotireoidismo (HIPO) e hipertireoidismo (HIPER) e &#945;2A-AR-/- de 21 dias de idade. Vimos que os animais &#945;2A-AR-/- apresentam menor comprimento no fêmur, tíbia, rádio, úmero e L4 quando comparados aos animais Selv. Como esperado, o HIPO e HIPER prejudicaram o CLO desses ossos nos camundongos Selv, entretanto, o efeito do HIPO foi mais deletério. A morfologia da LE distal do fêmur mostrou que os animais &#945;2A-AR-/- eutireóideos (EUT) apresentam desorganização de zonas e alterações no número de condrócitos sendo o Hipotireoidismo o tratamento mais deletérios. Dados desse estudos sugerem que as vias PTHrP/Ihh e IGF-1/IGF-1R possam ser vias de convergência do SNS e HT na regulação da morfofisiologia da LE, envolvendo o &#945;2A-AR. Observou-se que os animais &#945;2A-AR-/- apresentam alterações no osso trabecular com potencialização com o hipotireoismo. Além disso, os animais &#945;2A-AR-/- apresentam alterações a conectividade trabecular. Esses achados sugerem que o SNS e interage o HT dependente do &#945;2A-AR. / It is known that the thyroid hormone (TH) regulates the development and growth of bones. In the study, we investigated whether the HT interacts with the sympathetic nervous system (SNS) controlling bone longitudinal growth (CLO), and if this possible interaction depends on &#945;2A-AR -/-. Therefore, we evaluated the effect of 30 days of hypothyroidism (HYPO) and hyperthyroidism (HYPER) and &#945;2A-AR -/- 21 days old. We have seen that &#945;2A-AR -/- animals have shorter femur, tibia, radius, humerus and L4 compared to Selv animals. As expected, the HYPO and HYPER damaged the CLO of these bones in Selv mice, however, the effect of HYPO was more deleterious. The morphology of the distal femur LE showed that &#945;2A-AR -/- animals euthyroid (EUT) have clutter zones and changes in the number of chondrocytes and Hypothyroidism most harmful treatment. Data from this study suggest that PTHrP pathways / Ihh and IGF-1 / IGF-1R can be SNS convergence and HT pathways in the regulation of the CO morphophysiology involving the &#945;2A-AR. It was observed that &#945;2A-AR -/- animals show changes in trabecular bone with augmentation with the hipotireoismo. Furthermore, &#945;2A-AR-/- animals show changes trabecular connectivity. These findings suggest that the SNS and interacts the HT dependent &#945;2A-AR.

Objectives The purpose of this research was to describe the physical growth status, bone mineral content, areal bone mineral density, body composition, and metabolic risk level of children of Sudanese immigrant families, and to determine the relationship between these outcome measures and exposure to an adverse environment. Exposure was defined as the time spent in Sudan or neighboring countries and timing was defined as the age a child arrived in the USA. Two major modifying factors were considered; current nutritional status (food quality and food security) and current physical activity levels. Study Design and Methods This is a cross-sectional study conducted between July 2011 and April 2012. Subjects were recruited from the Iowa City, Iowa metropolitan area. The sample included 64 children between the ages of five and eighteen; 33 females and 31 males. Physical growth measures included weight, height, and BMI. Bone growth measures (body bone mineral content and areal bone mass density at the hip and spine) and body composition measures (lean mass, fat mass, and body fat percent) were measured using DXA. Metabolic risk factors included fasting blood glucose, low density lipoprotein (LDL), high density lipoprotein (HDL), total cholesterol, triglyceride, and C Reactive Protein (CRP) levels, and Homeostasis Model of Assessment Insulin Resistance (HOMA-IR). Physical activity was measured by self-report physical activity questionnaire for children and adolescents (modified PAQ-A and PAQ-C) and by direct measure using Omron Pedometers (HJ-720 IT). Other collected data included food quality, food security, food frequency, and pubertal development using a puberty developmental scale. Results The mean age for all children was 10.1 ± 3.3 years. More than half of the children (n=33, 51.6%) were born in the USA, 14 children (21.9%) were born in Sudan, and the other children were born in other countries. The majority of the children (63.6%) lived in low income households reporting annual income less than USD $19,000. Over one quarter (26.5%) of the children were overweight or obese as defined by BMI percentile and when categorized by BF%, 35.5% of the girls and 27.3% of the boys were identified as obese. Height stunting was noted with 4.7% severely stunted (more than 2 sd below the mean) and 9.4% moderately stunted (more than 1 sd below the mean). The mean Z score for FMI and LMI were -0.57 ± 1.51 and 0.49 ± 0.75, respectively, and neither was normally distributed. Around half of the children had FMIZ (53.1%) and LMIZ (47%) scores more than 1 SD below the mean. Median Z scores for all bone measures were negative; BMC, -0.71, hip aBMD, -0.53, and Spine aBMD, -0.13. Around one-third of the children fell more than 1sd below the mean for BMC (38%) and hip aBMD (33%). Metabolic risk factors were elevated in some subjects; high total cholesterol, 23.4%; high triglycerides, 32.8%; low HDL, 19%; high HOMA-IR and CRP levels, 15.6 %. Forty percent of participating families reported some level of food insecurity, and 31% reported skipping or cutting the size of meals due to inadequate food supplies. Both self-reported questionnaires and data collected from pedometers showed that the majority of study participants were inactive, Wednesday & Thursday were identified as the most active days with activity levels of 52.6% and 50.9%, respectively, and 40% of the study subjects were inactive on weekends. More than half (56.9%) of the subjects reported watching TV more than two hours per day. Children born in the USA had higher rates of height and weight stunting and obesity as compared to children born outside the USA (24%, 37.5%, 32.26%; 3.12%, 25%, 21.21%, respectively). Children born in the USA had lower Z scores in all bone and body composition measures. Using GEE analysis, longer residence in Sudan was associated with lower WAZ scores (β =-0.16, p= 0.07), and lower LMIZ scores (β =-0.05, p= 0.06). Children with longer residence in Sudan or neighboring countries had higher LDL and HOMA-IR levels (β =2.997, p= 0.0005), and (β =0.03, p= 0.08). Adjusting for gender, girls who spent more time in Sudan had higher triglyceride and CRP levels β =11.9, p=0.027) and (β =0.5, p=0.03), respectively. Children who were older when they entered the USA had higher HAZ scores (β =0.06, p=0.05). Adjusting for gender, Girls who arrived in the USA at a younger age had lower WAZ scores (β =-0.42, p=0.01), while girls who entered the USA at an older age had higher HOMA-IR, triglyceride, and CRP levels (β =0.29, p=0.005), (β =0.14, p= 0.05) and (β =0.5, p=0.05), respectively. Adjusting for number of years spent in the USA and physical activity levels, longer residence in Sudan was associated with poorer LMIZ (β =-0.06, p=0.001) and hip aBMD Z scores (β =0.11, p= 0.01). In addition, children who arrived in the USA at a younger age had higher height for age Z scores (β=0.094, p=0.005) and lower LMIZ scores (β =-0.09, p=0.04), respectively. Conclusion Sudanese children in the Iowa City metropolitan area, particularly those born in the USA, have low Z scores for physical growth, bone growth, and body composition measures. A significant percent of the children had high triglycerides and total cholesterol levels. The majority of Sudanese children were physically inactive and food insecurity was common.

Os impactos repetitivos decorrentes do esporte podem interferir no crescimento ósseo. Com o objetivo de tentar elucidar o efeito mecânico dos impactos repetitivos sobre a placa de crescimento ósseo, da tíbia proximal, um estudo experimental em ratos foi realizado. Inicialmente, foi desenvolvida uma máquina para a produção de impactos repetitivos na tíbia dos ratos. Os impactos repetitivos foram produzidos na tíbia direita em uma amostra de 60 ratos wistar, divididos em 6 grupos de 10 cada, sendo a esquerda o controle. A magnitude de impacto foi de aproximadamente 3,5 vezes a massa corporal dos ratos. Após os dias de impacto, os ratos foram sacrificados e as tíbias foram medidas. Em seguida um estudo histológico da placa de crescimento foi realizado. Foram medidas, a espessura total da placa de crescimento, a espessura da zona de repouso, de proliferação e hipertrófica e de calcificação juntas. Os resultados mostraram diferença significativa no comprimento da tíbia nos testes intra-grupos para os grupos 3, 4,e 5 (p≤0,05), e intergrupos para a tíbia direita e esquerda (p≤0,05). A placa de crescimento mostrou uma menor espessura significativa na tíbia direita (p≤0,05). Na esquerda não houve alteração significativa da espessura da placa (p=0,109). As zonas de repouso e proliferativa da placa da tíbia direita, e o número médio de células nas colunas da zona proliferativa apresentaram diferenças significativas intergrupos (p= 0,013, p=0,042 e p=0,017, respectivamente). As zonas hipertrófica e de calcificação apresentaram diferença significativas nas tíbias direita e esquerda (p 0,048 e 0=0,020, respectivamente). As análises múltiplas confirmaram que não existiram evidências de calcificação precoce da placa, com a magnitude de impacto produzida. Não houve mudança significativa nas zonas hipertrófica e de calcificação. A conclusão é de que os impactos repetitivos diminuem a espessura da placa de crescimento proximal da tíbia durante a puberdade, principalmente quando o tempo de impacto ultrapassa a metade do período de puberdade. Com a interrupção de 10 dias na produção dos impactos, permaneceu a diminuição da espessura da placa proximal da tíbia. A cargas de impactos de aproximadamente 3,5 vezes a massa corporal não são suficientes para exibir evidências de calcificação precoce da placa de crescimento. / The repetitive impact in exercise could make an interference in bone growth. In last years, it could be seeing an increase in children participation in sports and leagues. With the objective to try to understand the mechanical effect of repetitive impacts at growth plate, at proximal tibia, an experiment was made. Repetitive impacts was make at right tibia in a 60 wistar rats, with 6 groups with 10 rats each. The left tibia was the control. The magnitude of the impact was close to 3,5 of the corporal mass of the rats. After the impacts day, the animals was sacrifice and the tibias was measured. After that, an growth plate histological study was made. The total growth plate was measured, and also the resting zone, proliferative zone and hypertrophy and calcification together. Results shown a significative difference in tibia length in groups tests for groups 3,4 and 5 (p<0,05). The growth plate shows a significative small length at right tibia (p<0,05). The left tibia did not shown any siginificative alteration in it length at growth plate. (p=0,109). The resting and proliferative zones, the number of the columns cellules of the proliferative zone, show a significative difference between groups (p=0,013; p=0,042 and p=0,017). The hypertrophic and calcification zones shown a significative difference between right and left tibia (p=0,048 and p=0,020). The multiple analysis confirm that did not appear any evidence of precocious calcification, with that impact magnitude, even a reduce of total growth plate and proliferative zone.